Many industries conventionally employ thermal barrier coatings to thermally insulate an article. FIG. 1 represents a conventional thermal barrier coated article which typically comprises a metallic layer 5 beneath a thermal barrier coating, often a ceramic layer, 1, applied to a superalloy substrate 10. The ceramic layer, which reduces the surface temperature of the metallic substrate, is chosen based upon thermal conductivity, stability, expansion compatibility with the substrate, and thermocyclic compatibility. Industry typically employs yttria stabilized zirconia as the preferred ceramic layer.
The metallic layer, commonly referred to as a bond coat, functions as a bonding means between the ceramic layer and the substrate. Conventional metallic layers include nickel-aluminum systems which generally consist of a mixture of gamma and beta phases, or the intermetallic compound nickel aluminide (NiAl). Gamma represents the solid solutions of the elements nickel, aluminum, chromium, cobalt, and the other elements that comprise the nickel base superalloys, while beta represents the intermetallic compound of nickel and aluminum frequently modified by the elements commonly present in the superalloys and often alloyed with special elements such as platinum and other precious metal elements.
The interface between the metallic layer and the ceramic layer is typically an oxide scale, such as alumina scale, which bonds the two layers together. Premature failure of these thermal barrier coatings is typically associated with chipping or breaking up (spallation) of the oxide scale. What is needed in the art is an improved thermal barrier coated article which is resistant to delamination of the thermal barrier coating due to oxide scale spallation.